Well, there’s a bunch of reasons, but basically:
a) Not everyone in Korea is gonna run out to buy a new computer just to play Starcraft 2. Starcraft 1 could run on any computer. Starcraft 2 can’t.
b) It’s not as good or as balanced as Brood War (when adjusted for period it came out) - there’s a real reason for this, which is that Blizzard put “e-sports” first and game quality second, and it really does show. Maybe Brood War was an accidental masterpiece or whatever, but they didn’t even try for this one.
c) They pissed off KeSPA, which is an organization that holds all the cards when it comes to televised gaming, by shutting them out and signing an exclusive contract with their (smaller) competitor, GomTV, which, despite the name, doesn’t actually hold any broadcasting rights but is a streaming service.
d) No LAN; internet cafes are not going to pay $3000 for their 50 computers just so their customers can play 1 game. All the Korean kids who are forced to study for 10 hours a day are not going to convince their parents to buy them a new computer plus Starcraft 2 so they can bring shame to the family or whatever, so the only other place where they could possibly play won’t have it.
Blizzard’s not releasing their sales figures in South Korea. Unless it’s embarrassingly low, I don’t see any reason why they would hide it.